In the refining of petroleum products, such as crude oil, hydrochloric acid is generated which can cause high corrosion rates on the distillation unit metallurgy. Neutralizing amines are added to the overhead system to neutralize the HCl and make it less corrosive. Excess amines can form salts that will lead to corrosion. Consequently, the refining industry has, for many years, suffered from amine-hydrochloride salt deposition in crude oil towers. The problem occurs when ammonia and/or amines are present in the desalted crude. These amines react with hydrochloric acid and other acids while ascending the crude tower and deposit as corrosive salts in the tower and the top pumparound equipment. The amines can be present from several sources, including but not necessarily limited to, crude oil (e.g. H2S scavenger chemicals), slop oil (frequently containing gas scrubbing unit amines) and desalter wash water (often composed of overhead sour water containing amine neutralizer). The problem has worsened in recent years in part due to higher crude salt content, which yields higher HCl and requires more overhead neutralizer, consequently both salt reactants are present in higher quantities. Additionally, many crude towers are operated at colder top temperature, which further encourages salt formation in towers. Longer run cycles between turnarounds have caused the problem to become a priority. Clearly, amine salting in towers has become a bigger problem in recent years, and future trends indicate continuation of the problem.
Solutions examined thus far fall into two categories. First, for cases where the amine is coming in with the crude oil or slop oil, the primary option is to segregate the offending streams and keep them out of the crude unit. This approach is economically unattractive in many cases. Second, in cases where the problem occurs due to recycle of overhead neutralizer, the approach has been to switch to overhead amines that will not form a salt at tower conditions. This technique is also economically unattractive in most applications, since these alternative neutralizers cost from three to four times as much as the conventionally used amines.
Additional changes are foreseen which are likely to make the problem even worse. The nature of “opportunity crudes” and crude quality in general are deteriorating, and further, more plants are attempting to maximize internal water reuse. A recent effort to design new amine neutralizer options for overhead systems does not offer much relief because, as noted, the amine options identified are higher cost raw materials. Even if alternative amines are identified at reasonable costs, such amines will not help in systems where tramp amines enter the system with crude oil or slop oil.
It would be desirable if methods and/or compositions could be devised that would remove, reduce, eliminate, take out or otherwise remove amines and/or ammonia from these hydrocarbon streams, as well as reduce, alleviate or eliminate corrosion caused by undesired amine salts where amines enter refinery towers.